The true God, however, neither employs irrational animals, nor any individuals whom chance may offer, to convey a knowledge of the future; but, on the contrary, the most pure and holy of human souls, whom He inspires and endows with prophetic power. And therefore, whatever else in the Mosaic writings may excite our wonder, the following must be considered as fitted to do so: “You shall not practise augury, nor observe the flight of birds;” and in another place: “For the nations whom the Lord your God will destroy from before your face, shall listen to omens and divinations; but as for you, the Lord your God has not suffered you to do so.” And he adds: “A prophet shall the Lord your God raise up unto you from among your brethren.” On one occasion, moreover, God, wishing by means of an augur to turn away (His people) from the practice of divination, caused the spirit that was in the augur to speak as follows: “For there is no enchantment in Jacob, nor is there divination in Israel.
In due time will it be declared to Jacob and Israel what the Lord will do.” And now, we who knew these and similar sayings wish to observe this precept with the mystical meaning, viz., “Keep your heart with all diligence,” that nothing of a demoniacal nature may enter into our minds, or any spirit of our adversaries turn our imagination whither it chooses. But we pray that the light of the knowledge of the glory of God may shine in our hearts, and that the Spirit of God may dwell in our imaginations, and lead them to contemplate the things of God; for “as many as are led by the Spirit of God, they are the sons of God.”
Source: Against Celsus (New Advent)